Hydrophobic and icephobic coating

ABSTRACT

Embodiments described herein relate to layered structures having a top surface which is hydrophobic for reducing the wetting of water or ice on the layered structure without requiring reapplication. In one or more embodiments, a layered structure is provided and includes a coating containing silicon, oxygen, and carbon disposed over a substrate and an interface disposed between the substrate and the coating. The substrate is at least partially transparent to visible light, a concentration of carbon in the coating is greater at a top surface of the coating than the interface, and the top surface of the coating is disposed on the opposite side of the coating than the interface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.16/795,431, filed Feb. 19, 2020, which claims benefit to U.S. Prov.Appl. No. 62/820,648, filed Mar. 19, 2019, which are hereby incorporatedby reference in their entirety.

BACKGROUND Field

Embodiments of the invention relate to a method and an article ofmanufacture and, more specifically, to a method of depositing ahydrophobic and icephobic coating.

Description of the Related Art

Glass surfaces are hydrophilic by nature, such that glass surfaces tendto attract water, resulting in formation of a water film or ice film onthe surface. In snowy, winter weather, cars and other vehiclesaccumulate ice, which is especially problematic on windshields, windowsand other viewing surfaces. Additionally, during rain, water filmsforming on windshields impair visibility during driving.

In order to combat this issue, current solutions in the marketplaceinclude heated windshield wipers to help melt snow, and sheets ofplastic to cover the windshields to prevent snow formation. However,heated windshield wipers are energy intensive, take a long time toremove snow, and often convert snow into hard ice before final removal.Plastic sheet covers have to be repeatedly applied and removed and oftentrap ice underneath.

Silicone based liquid formulations are found in the art, which preventice and snow buildup by providing a temporary hydrophobic coating,lessening the sticking of ice and snow to the windshield or other glasssurfaces. One drawback of these coatings is that the coatings aretemporary and have to be reapplied every few weeks, making them costlyand time consuming.

Therefore, there is a need for long-lasting hydrophobic and icephobiccoating of windshields and other glass surfaces.

SUMMARY

In one embodiment, a method of depositing a coating is provided,including depositing the coating on a substrate, the coating includingsilicon (Si), oxygen (O), and carbon (C). The substrate is at leastpartially transparent to visible light. The coating is deposited suchthat an interface is formed between the substrate and the coating. Theconcentration of C in the coating is larger at a top surface of thecoating than the interface. The top surface of the coating is disposedon the opposite side of the coating than the interface.

In another embodiment, a method of depositing a coating is provided,including depositing the coating on a substrate, the coating includingsilicon (Si), oxygen (O), and carbon (C). The substrate is at leastpartially transparent to visible light. The coating is deposited suchthat an interface is formed between the substrate and the coating. Theconcentration of C in the coating is larger at a top surface of thecoating than the interface. The top surface of the coating is disposedon the opposite side of the coating than the interface. Theconcentration of C in the coating ranges from about 3 atomic percent toabout 25 atomic percent.

In another embodiment, a layered structure is provided, including asubstrate and a coating disposed over the substrate. The coatingincludes silicon (Si), oxygen (O), and carbon (C). The substrate is atleast partially transparent to visible light. The coating is depositedsuch that an interface is formed between the substrate and the coating.The concentration of C in the coating is larger at a top surface of thecoating than the interface. The top surface of the coating is disposedon the opposite side of the coating than the interface.

The top surface of the coating in the layered structure is inherentlyhydrophobic and icephobic, and thus the coating at least partiallyprevents the wetting of a water or ice film on the surface of thelayered structure. The coating does not to be periodically replaced, andthus the substrate, such as a windshield or window, does not need to beretreated.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the presentdisclosure can be understood in detail, a more particular description ofthe embodiments, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this disclosure and are therefore not to beconsidered limiting of its scope, for the disclosure may admit to otherequally effective embodiments.

FIG. 1 is a flow diagram of method operations for depositing a coatingon a substrate, according to one embodiment.

FIG. 2A illustrates a layered structure, according to one embodiment.

FIG. 2B illustrates the layered structure of FIG. 2A during depositionof a coating, according to one embodiment.

FIG. 2C illustrates the layered structure of FIG. 2B undergoingpost-treatment, according to one embodiment.

FIG. 3 illustrates a treated windshield in a car, according to oneembodiment.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements and features of oneembodiment may be beneficially incorporated in other embodiments withoutfurther recitation.

DETAILED DESCRIPTION

Embodiments of the disclosure provided herein include a method ofcoating a substrate, and a layered structure created by coating thesubstrate. A coating including silicon (Si), oxygen (O), and carbon (C)is deposited on a substrate. The top surface of the coating isinherently hydrophobic and icephobic. There is a variation in C dopingin the coating, so that unwanted reflections, refractions, or diffusionof visible light through the layered structure is not negativelyaffected by the coating. In addition, the gradual variation of C dopingthrough the coating allows for good adhesion at the interface betweenthe surface and the coating. Embodiments of the disclosure providedherein may be especially useful for, but are not limited to, a method ofdepositing a coating on a substrate transparent to visible light.

As used herein, the term “about” refers to a +/−10% variation from thenominal value. It is to be understood that such a variation can beincluded in any value provided herein.

FIG. 1 is a flow diagram of method operations 100 for depositing acoating on a substrate to create a layered structure, according to oneembodiment. Although the method operations are described in connectionwith FIGS. 1 and 2A-C, persons skilled in the art will understand thatany system configured to perform the method operations, in any order,falls within the scope of the embodiments described herein. FIG. 2Aillustrates a layered structure 200, according to one embodiment. Thelayered structure 200 includes a substrate 205. The substrate 205includes silicon (Si) and oxygen (O), according to one embodiment. Thesubstrate 205 allows the passage of at least a portion of the spectrumof visible light. The substrate can include glass. The substrate 205 canbe an optical lens of any kind, including a lens for magnifying orcorrecting any aberration of an image, such as spherical or chromaticaberrations. The substrate 205 can be a lens for eyeglasses or goggles.The substrate 205 can be a layered structure, and can include layers orother features for partially or completely blocking a spectrum of light,such as infrared, ultraviolet, and the like.

The substrate 205 is a windshield for a vehicle, according to oneembodiment. The substrate 205 is a side or rear window for a vehicle,according to one embodiment. The vehicle can be, but is not limited to,a car, a truck, a motorcycle, a boat, a ship, a scooter, a train, anamphibious vehicle, an aircraft, an airplane, a helicopter, aspacecraft, and the like. The substrate 205 is a window for a building,a permanent structure, or a temporary structure, according to oneembodiment.

Referring to FIGS. 1 and 2A-C, the method begins at operation 110, wherea coating 215 is deposited on the substrate 205. FIG. 2B illustrates thelayered structure 200 of FIG. 2A during deposition of the coating 215,according to one embodiment. The coating 215 can be deposited by anyconventional deposition process 210, such as, but not limited to, atomiclayer deposition (ALD), physical vapor deposition (PVD), and chemicalvapor deposition (CVD). The deposition process 210 can be performed inany conventional deposition chamber (not shown). The precursors can beany precursor or combination of precursors that contain carbon, oxygen,and silicon. The deposition process 210 can be performed at atemperature from between about 300° C. to about 450° C. The process canbe performed from about 60 seconds to about 10 minutes. A radiofrequency (RF) can be applied with an RF power of about 400 W to about800 W. Pressure of the chamber (not shown) can be maintained at about 5Torr to about 10 Torr. A neutral gas, such as argon (Ar) or helium (He),can be co-flowed during deposition at a flow rate of about 2000 sccm toabout 5000 sccm.

In one embodiment, the deposition process 210 is CVD, the precursors areoctamethylcyclotetrasiloxane (OMCTS), methane (CH₃), and oxygen gas(O₂), oxygen gas is provided at a flow rate of about 50 sccm to about200 sccm, helium gas (He) is co-flowed during deposition at a flow rateof about 2000 sccm to about 5000 sccm, pressure of the chamber (notshown) can be maintained at about 5 Torr to about 10 Torr, and theprocess is performed at a temperature of about 350° C., with an appliedRF power of about 400 W to about 800 W. Carbon in the coating 215 isdeposited at rate of about 4000 Å/min to about 5000 Å/min. Higher RFpower leads to lower carbon content, so in one embodiment, growth of theinterface 225 is performed at a higher RF power, which is then graduallyreduced during the course of deposition to form a variation in thecarbon content of the coating 215.

The coating 215 includes silicon (Si), oxygen (O), and carbon (C). Thecoating can also include hydrogen (H). An interface 225 is formedthrough chemical bonding between the coating 215 and the substrate 205.The C can bond to Si, substituting O, by forming terminal methyl groups(—CH₃). The C can substitute for 0 in the bonded Si—O network by formingmethylene bridges (—CH₂—) between Si atoms, or the C can substitute forSi in the bonded Si—O network as C. The aforementioned C groups are alsolocated at the top surface 215S of the coating 215, and the C groupsreduce contact angle of water droplets disposed on the top surface. Thetop surface 215S is inherently hydrophobic, such that water contactangles of water droplets is between about 90° to about 120°, accordingto one embodiment. The top surface 215S is also icephobic, such that iceis at least partially prevented from forming on the top surface.

It is known in the art that hydrophobic and icephobic surfaces at leastpartially prevent the sticking of water and ice to the surface via wateror ice film growth, which makes removal of water and ice easier. A watercontact angle of water droplets between about 90° to about 120° leads toabout 50% of the ice or water sticking to the surface of a material.Thus, the top surface 215S reduces the wetting of a water film or an icefilm. The top surface 215S is hydrophobic and icephobic as deposited,and thus does not require retreating, which results in decreased costand time for the user.

The coating 215 includes from above about 0 atomic percentage of C tobelow about 40 atomic percentage of C, such as about 3 atomic percentageof C to about 25 atomic percentage of C, preferably about 2 atomicpercentage of C to about 12 atomic percent carbon, according to oneembodiment. The C concentration in the coating 215 is variable, suchthat the concentration of C in the coating is larger at the interface225 than at a top surface 215S of the coating, wherein the top surfaceof the coating is disposed on the opposite side of the coating than theinterface. The variation of concentration of C in the coating 215 issubstantially linear between the interface 225 and the top surface 215S,according to one embodiment. The gradual variation of concentration of Callows for a smooth variance in the index of refraction of the coating215, preventing large amounts of light from being reflected, refracted,diffracted, or otherwise undesirably altered, so as to provide unimpededvision through the layered structure 200. Thus, the index of refractionof the substrate 205 and the layered structure 200 can be similar.

The gradual variation of concentration of C allows for a clean interface225 between the substrate 205 and the coating 215, preventing formationof vacancies or interstitial atoms at the interface which cause unwantedreflection, refraction, or diffraction of light through the layeredstructure 200. In this manner, the concentration of C in the coating 215gradually increases until it reaches its desired value at the topsurface 215S, which is below about 25 atomic percentage of C, preferablyabout 3 atomic percentage of C to about 12 atomic percentage of C, andthe C groups present at the top surface contribute to the hydrophobicityand icephobicity of the coating. The thickness of the coating 215 isfrom about 100 Å to about 10 μm, preferably from about 100 Å to about 5μm, according to one embodiment. Thinner coatings 215 are preferable, asthere is minimal impact to optical or “see thru” performance of glass,but too thin of coatings can wear off over time due to mechanical wearfrom erosion or windshield wiper or other cleaning operations, leadingto growing the coating at a thickness as descried above.

The layered structure 200 has an acceptable bulk modulus and hardness sothat the layered structure has acceptable strength for the purpose ofthe layered structure, e.g., strong enough for use as a windshield orside window in vehicles. The bulk modulus of the layered structure 200can vary between about 5 GPa to about 40 GPa, and the hardness of thelayered structure can vary between about 1 GPa to about 10 GPa,depending on the use of the layered structure as a windshield or window.The refractive index of the coating 215 is similar to the substrate 205,or the difference is minimal for ideal optical performance. The index ofrefraction for glass is about 1.45, and the refractive index of thecoating 215 is expected to be lower, a gradual change in refractiveindex while minimizing total film thickness will result in ideal opticalperformance. The maximum difference in refractive indices should bemaintained below about 0.2, in order to maintain desired opticalperformance of the layered structure 200.

At optional operation 120, a post-treatment 220 is applied to thelayered structure 200. The post-treatment 220 can include an anneal, abake, a chemical etch, a chemical cleaning process, or any combinationof the above, performed either sequentially or simultaneously. FIG. 2Cillustrates the layered structure 200 of FIG. 2B undergoingpost-treatment 220, according to one embodiment. The post-treatment 220improves uniformity of the coating 215, heals atomic vacancies in thecoating, the substrate 205, and the interface 225, ensures a smootherinterface between the substrate and the coating, and improves topsurface 215S smoothness, all of which improves the optical andstructural properties of the layered structure 200.

The layered structure 200 can include multiple layers of substrates 205and coatings 215. A film can be grown on a layered structure 200, andthe film becomes the new substrate 205 upon which method 100 can beperformed. In this manner, the method 100 can be performed repeatedly,resulting in multiple layers of substrates 205 and coatings 215. Avacuum or air gap can be present between iterations of the layeredstructure 200, as in, for example, double pane windows or windshields.The layered structure 200 can be laminated glass, and the iterations ofsubstrates 205 and coatings 215 can be separated by an interlayer, sothat the layered structure holds together when shattered. The interlayercan include polyvinyl butyral (PVB), ethylene-vinyl acetate (EVA),polybutylene terephthalate (PBT), or the like.

FIG. 3 illustrates a treated windshield 326 in a vehicle 300, accordingto one embodiment. Although FIG. 3 shows the vehicle 300 is a car, thevehicle can be any of the vehicles presented above, although not limitedsolely to the vehicles presented above. The windshield frame 354 isdisposed in an aperture in the vehicle 300, and the treated windshield326 is attached to the windshield frame by fasteners 360. The fasteners360 can be any used in the art to fasten windshields to the vehicle 300in the art, such as clips, molding, weather stripping, and the like. Thesubstrate 205 is a conventional windshield, and thus the treatedwindshield 326 is the layered structure 200, according to oneembodiment, and the coating 215 increases the hydrophobicity andicephobicity of the treated windshield surface. The coating 215 preventsbuild-up of ice and snow, and allows for easier removal of the ice andsnow from windshield wipers. The small thickness of the coating 215 incomparison to the thickness of a conventional windshield allows thecoating to be applied to a conventional windshield without necessitatingredesign or further engineering of the windshield, since the smallthickness of the coating does not interfere with many designs offastening windshields to vehicles.

As described above, a coating 215 is deposited on a substrate 205 tomake a layered structure 200. The substrate 205 can be a windshield, andthus the layered structure 200 is a treated windshield 326. The coating215 includes silicon, oxygen, and carbon, where the carbon doping in thecoating increases between the interface 225 and the top surface 215S ofthe coating.

The top surface 215S of the coating 215 is inherently hydrophobic andicephobic, and reduces the wetting of water or ice film on the layeredstructure 200, without requiring reapplication of the coating. Thecoating 215 can be deposited on conventional glass substrates 205, suchas a windshield or window. The gradual variation in carbonconcentrations in the coating 215 results in slowly varying index ofrefraction, which reduces unwanted refraction, reflection, ordiffraction of light passing through the layered structure 200.

While the foregoing is directed to implementations of the presentinvention, other and further implementations of the invention may bedevised without departing from the basic scope thereof, and the scopethereof is determined by the claims that follow.

What is claimed is:
 1. A layered structure, comprising: a coatingcomprising silicon, oxygen, and carbon disposed over a substrate; and aninterface disposed between the substrate and the coating; wherein: thesubstrate is at least partially transparent to visible light; aconcentration of carbon in the coating is greater at a top surface ofthe coating than the interface; and the top surface of the coating isdisposed on the opposite side of the coating than the interface.
 2. Thelayered structure of claim 1, wherein the concentration of carbon in thecoating is greater at the top surface of the coating by reducing a radiofrequency power as the coating is deposited from the interface to thetop surface.
 3. The layered structure of claim 1, wherein theconcentration of carbon in the coating is less than 40 atomic percent.4. The layered structure of claim 1, wherein the coating on thesubstrate was deposited by a chemical vapor deposition process.
 5. Thelayered structure of claim 1, wherein the coating has a hardness in arange from about 1 GPa to about 10 GPa.
 6. The layered structure ofclaim 1, wherein the coating has a bulk modulus in a range from about 5GPa to about 40 GPa.
 7. The layered structure of claim 1, wherein aplurality of water droplets disposed on the top surface of the coatingmakes a water contact angle with the top surface, the water contactangle is in a range from about 90° to about 120°.
 8. The layeredstructure of claim 1, wherein the thickness of the coating is in a rangefrom about 1,000 Å to about 10 μm.
 9. The layered structure of claim 1,wherein the variation of concentration of carbon in the coating issubstantially linear between the interface and the top surface.
 10. Thelayered structure of claim 1, wherein the concentration of carbon in thecoating is in a range from about 3 atomic percent to about 25 atomicpercent.
 11. The layered structure of claim 1, wherein the substratecomprises a windshield for a vehicle.
 12. The layered structure of claim1, wherein the substrate comprises silicon and oxygen.
 13. The layeredstructure of claim 1, further comprising a second substrate disposedabove the coating, the second substrate and the coating are separated bya non-zero distance or an interlayer.
 14. The layered structure of claim13, further comprising a second coating formed over the secondsubstrate.
 15. A layered structure, comprising: a coating comprisingsilicon, oxygen, and carbon disposed over a substrate; and an interfacedisposed between the substrate and the coating; wherein: the substrateis at least partially transparent to visible light; a concentration ofcarbon in the coating is greater at a top surface of the coating thanthe interface; the top surface of the coating is disposed on theopposite side of the coating than the interface; the thickness of thecoating is in a range from about 1,000 Å to about 10 μm; the coating hasa hardness in a range from about 1 GPa to about 10 GPa; and the coatinghas a bulk modulus in a range from about 5 GPa to about 40 GPa.
 16. Thelayered structure of claim 15, wherein the concentration of carbon inthe coating is greater at the top surface of the coating by reducing aradio frequency power as the coating is deposited from the interface tothe top surface.
 17. The layered structure of claim 15, wherein aplurality of water droplets disposed on the top surface of the coatingmakes a water contact angle with the top surface, the water contactangle is in a range from about 90° to about 120°.
 18. The layeredstructure of claim 15, wherein the substrate comprises a windshield fora vehicle.
 19. The layered structure of claim 15, further comprising asecond substrate disposed above the coating, the second substrate andthe coating are separated by a non-zero distance or an interlayer.
 20. Alayered structure, comprising: a coating comprising silicon, oxygen, andcarbon disposed over a substrate; and an interface disposed between thesubstrate and the coating; wherein: the substrate is at least partiallytransparent to visible light; the thickness of the coating is in a rangefrom about 1,000 Å to about 10 μm; a concentration of carbon in thecoating is greater at a top surface of the coating than the interface byreducing a radio frequency power as the coating is deposited from theinterface to the top surface; and the top surface of the coating isdisposed on the opposite side of the coating than the interface.